Wellesley Petroleum and its partners have made a gas-condensate and oil discovery in licence PL1148 in the Norwegian North Sea.

The discovery follows the drilling of exploration well 35/10-10 S and appraisal sidetrack well 35/10-10 A, located around 25km northwest of the Troll field and 150km north-west of Bergen.

The wells, which have been drilled using the Deepsea Yantai rig, were targeting the Carmen prospect.

Following the drilling, the Well 35/10-10 S identified a 210m gas-condensate column in the Ness, Etive and Oseberg formations. Of this, 90m is in sandstone layers with poor-to-good permeability.

The partners also discovered a 70m gas-condensate column in the Cook Formation, 23m of which is in sandstone with poor permeability, as well as a 13m light oil column in sandstone in the Early Jurassic Amundsen Formation.

Well 35/10-10 A, following drilling, encountered a 240m gas and volatile oil column in the Ness, Etive, Oseberg and Cook formations. Of this, 50m is in sandstone layers with generally poor permeability.

Furthermore, the well identified water-filled sandstone of good reservoir quality in the Cook Formation.

In a statement, Wellesley said: “Additionally, information from the 35/10-A appraisal well indicates the possibility for significant upside volumes, with up to 300mboe [million barrels of oil equivalent] potentially being recoverable in and around the accumulation, subject to successful exploration and appraisal activity.”

As per the Wellesley estimates, the drilling campaign has proved a developable gas-condensate accumulation of 60–100mboe.

Wellesley CEO Chris Elliott said: “Carmen is Wellesley’s sixth commercial discovery in our core Troll area portfolio, and once again validates our geological model for the Middle Jurassic play.

“Carmen is well positioned to join and add value to the ongoing area development programme for the other recent discoveries in the greater Troll area. Wellesley will use the early phase development experience gained from our stewardship of the Grosbeak discovery to move the Carmen project forward efficiently.

“Additionally, we will begin studies to understand the potentially significant upside potential, which may include further exploration and appraisal drilling activity.”

The two wells mark the first and second exploration wells in production licence 1148, awarded in APA2021 (Awards in Predefined Areas 2021).

The Deepsea Yantai drilling facility is now due to drill wildcat well 25/7-11 S in production licence 984 in the North Sea.